1. Field of the Invention
This invention relates to the slitting of a traveling fibrous web, particularly a paper web. More particularly, this invention relates to the slitting of a traveling paper web utilizing both a water jet and a laser. Still more particularly, this invention relates to the efficient slitting of a traveling paper web utilizing a water jet to sever the web, and a laser to cut the edges to produce a smooth edge on the severed parts.
2. Description of the Prior Art
The use of a high pressure water jet to cut a traveling web, such as paper, into strips is known in the papermaking art. Also known is the use of a laser beam to cut a fibrous web, such as paper. Both of these devices have been tried in an effort to improve the slitting results provided by a pair of cooperating rotating disks which have outer edges that rotate toward one another and intersect over the oncoming web passing therebetween to effect the cutting operation. Such disk- type slitters are well-known and represent the standard in the papermaking industry.
However, there are deficiencies and operating inefficiencies associated with the use of cooperating disks, lasers and high pressure water jets to effect the web slitting operation. In the case of cooperating disks, a great deal of dust is produced as the blades tear individual fibers from the paper web during the slitting process. In addition, disk slitters tend to produce edge cracks extending laterally in the paper being slit which, in turn, promotes lateral tearing and sheet breaks in the winding process on a papermaking machine or, even worse, during the printing process in the paper manufacturer's customer's plant. Finally, disk-type slitters require continual sharpening and/or replacement of the disks and must have transport and holder assemblies on both sides of the traveling web for each of the disks.
Perhaps the greatest deficiency in using water jets to slit a traveling paper web, especially a completely dried web, such as is the case in the winder, resides in the inherent nature of the severing process using a water jet. Specifically, the high pressure jet stream of water effects the web severance by impacting the individual paper fibers in the web. The actual severance is thus accomplished by physically pushing fillers, fines and individual fibers from the spot of jet stream impact outwardly toward the far surface and away from the web. Individual wood pulp fibers are not cut into pieces, but instead have fines, fillers and even small, or short, fibers washed away by the impact of the high pressure water jet. This leaves the ends of individual wood pulp fibers protruding from each severed edge of the web. The water jet cut results in a somewhat ragged pair of edges on either side of the slit in the web. This is both aesthetically unappealing, deleterious to subsequent processing of the paper product and generally undesirable to both the paper manufacturer and its customers.
In the case of a laser, the slit produced in the traveling web is well defined with a smooth, continuous edge from the standpoint of having few or no fiber ends protruding from the edge of the web. However, lasers powerful enough to cut a web at the speeds and calipers encountered in the paper manufacturing or winding operation tend to be relatively expensive to operate.